Fabrication of semiconductor integrated circuits and flat panel displays involves numerous processes, such as etching, chemical vapor deposition, sputtering and cleaning, which are performed on semiconductor and flat panel display substrates. Each of these processes may be performed using a different single processing tool, i.e., a tool that performs a single fabrication process. Since multiple fabrication processes must be performed, the substrates must be transferred from one processing tool to the next, which exposes the substrates to potential contamination. In addition, transferring substrates between different processing tools increases the overall processing time.
Consequently, multiple processing tools have been developed that can perform multiple fabrication processes. A multiple processing tool, which is typically known in the semiconductor and FPD industry as a “cluster tool”, includes multiple process chamber units arranged in a circular pattern connected to a single vacuum transfer chamber with one vacuum transfer robot to transfer substrates between the multiple process chamber units and single or dual load lock chambers. Since substrates are transferred within a single tool for different fabrication processes, the potential for contamination is reduced. In addition, the substrates can be more quickly transferred between process chamber units, which reduces the overall processing time.
A concern with conventional multiple processing tools is that system performance and reliability are greatly reduced by potential failure of the single vacuum transfer robot located inside the vacuum transfer chamber. Although fabrication processes can be continued by the vacuum process chamber units, the failure of the vacuum transfer robot limits the transferring of the substrates thereby causing system downtime. However, there are also conventional tools in which the transfer robots are located in an atmospheric environment while the process chamber units perform fabrication processes in a vacuum environment. Thus, in these multiple processing conventional tools, a vacuum environment must be created repeatedly in some of these process chamber units when substrates are transferred into and out of the process chamber units. This increases complexity and manufacturing cost of these multiple processing tools, as well as the overall processing time.
Thus, there is a need for an apparatus and method for processing substrates that reduces the complexity and manufacturing cost of the apparatus, as well as the overall processing time, while increasing system reliability and up-time.